The present invention relates to a drive unit for fans in vehicles, comprising a brushless direct current motor and an electronic actuation system.
A fan for vehicles with a drive unit that has a brushless direct current motor with an external rotor is already known from U.S. Pat. No. 5,588,814. The drive unit of this fan is integrated into a collecting and distributing box, which surrounds the fan wheel. The external rotor, which is combined with the fan wheel to form a structural unit, is mounted on base parts of the collecting and distributing box. The air sucked in by the fan wheel is directed against the drive unit. A cooling air flow that is derived from the sucked-in air is fed to power semiconductors of the electronic actuation system, the power semiconductors being mounted on a circuit board situated below the drive unit.
The drive unit according to the invention for a fan in a vehicle is an autonomous assembly that does not require any structural parts on the collecting and distributing box in order to mount the direct current electric motor or to accommodate the electronic actuation system. According to the invention, the electronic actuation system is surrounded by a housing made of plastics that supports the electric motor. Since the drive unit forms an autonomous assembly, it can be combined with all kinds of housing parts and fan wheels to constitute a fan. The housing surrounding the electronic actuation system is installed on the suction side of the fan so that the sucked-in air can be fed through inlet openings in the housing and can be used to cool the power semiconductors of the electronic actuation system as well as the components of the electric motor.
In a preferred embodiment of the drive unit, the housing has an integrally molded bearing sleeve for mounting the rotor of the electric motor, which has an external rotor. The bearing sleeve accommodates the bearings for mounting the journal of the external rotor. It also forms a guide channel for the cooling air flow that is needed for cooling the power semiconductors of the electronic actuation system and that can enter through air inlet openings of the housing, parallel to the air flows between the rotor and the stator of the electric motor resulting from the pressure differential between the suction side and the pressure side of the fan.
According to another advantageous embodiment of the invention, the electronic actuation system has a power part and a control part, which are mounted on separate circuit boards, the circuit board for the power part being made in that a conductor structure stamped out of sheet metal is encapsulated with plastic by means of injection-molding. Therefore, the power part can handle extremely high currents without endangering the sensitive components on the printed circuit board of the control part.